Yeah, I was kinda dumb posting those links thinking they're not simulations. But there are some algorithms for terrain generation that I heard of, which I think was either posted here or in the SE development thread before.I found this erosion technique, maybe it's faster than simulating water flow.http://www.fracterra.com/FunWithWilburVol1/index.html
Space engine could really use an erosion filter for more complex, accurate terrain
http://arches.liris.cnrs.fr/publications/SIG2013.html